#include <stdio.h>
int main(void)
{
        double s =0, f=1;                                                
        int n, i=1;
        scanf("%d", &n);
        while(i<=n)                                                        
        {
            s+=f/i++;                
            f=-f;                                                              
        }
        printf("%f",s);
        return 0;
}
